Currently used methods for preparing high density products, such as flanges, of stainless steel powders involve compacting the stainless steel powders to densities of between about 6.4 and 6.8 g/cm3 at compaction pressures of 600-800 MPa. The obtained green body is then sintered at high temperatures, i.e. temperatures up to 1400° C. for 30 to 120 minutes in order to get densities of about 7.25 g/cm3. The requirement for the long sintering times at the comparatively high temperatures is of course a problem considering the high energy costs. The necessity for special, high temperature furnaces is another problem.
A recently developed method of achieving high sintered densities in sintered stainless steel parts is disclosed in the WO patent publication 99/36214. According to this method a gas atomised metal powder having spherical particles is agglomerated with at least 0.5% by weight of a thermo-reversible hydrocolloid as a binder. The agglomerated composition is then compacted in a uniaxial press operation with a ram speed of over 2/s to a green body having a high density. When the metal powder is a stainless steel powder the publication recommends sintering at 1350° C. for 2 to 3 hours in order get high sintered densities.